The present invention relates generally to line scan cameras, and more particularly to a new and improved line scan camera which comprises a sealed camera structure or entity wherein an optical assembly, which comprises or includes a lens and CCD subassembly, and an optical bench assembly, which comprises or includes the focal point or object plane, are integrated together such that once the optical assembly is calibrated and locked in position with respect to the optical bench assembly by means of highly skilled factory technicians, further calibration or recalibration of the optical assembly, or more particularly, the lens and CCD components, with respect to each other as well as with respect to the optical bench assembly, or more particularly, with respect to the object plane, is no longer required. In addition, dust and other contaminants are effectively substantially prevented from entering the sealed camera structure so as not to collect upon the optical components of the camera whereby substantial maintenance or cleaning of the optical components of the camera is not usually required. Should routine maintenance or cleaning of the optical components of the camera nevertheless be required, such routine maintenance or cleaning of the optical components of the camera, and reassembly of the entire sealed camera structure, can be rapidly performed, with minimal operational downtime of the camera, due to the fact that recalibration of the optical assembly, with respect to the optical bench assembly, is obviated despite the fact that the various optical components of the camera were operatively disassembled with respect to each other.
Line scan cameras are used in various industrial or commercial applications, such as, for example, in those instances or circumstances wherein the camera is maintained stationary while the objects to be photographed or scanned are moved with respect to the camera. One such exemplary industrial or commercial application comprises the use of line scan cameras in connection with the high-speed sorting or processing of mail. In accordance with such systems, for example, pieces of mail are conveyed past a point or object plane at which the line scan camera scans or photographs the same. In order to achieve the necessary high-speed scanning or photographing of the mail so as to, in turn, ensure the high-speed processing or sorting of the millions of pieces of mail which enter the mail or postal system on a daily basis, it can be readily appreciated that relatively simple, accurate, high-speed, and reliable line scan cameras, devices, or systems are required. Prior art or conventional line scan cameras, or similar devices or systems, are exemplified by the devices or systems which are disclosed, for example, within U.S. Pat. No. 5,986,253 which issued to Tabata on Nov. 16, 1999, U.S. Pat. 5,936,239 which issued to Tsai et al. on Aug. 10, 1999, U.S. Pat. No. 5,883,386 which issued to Tsuyuki et al. on Mar. 16, 1999, and U.S. Pat. No. 5,661,297 which issued to Aleshire et al. on Aug. 26, 1997. While these prior art line scan cameras, or devices or systems, have ostensibly been satisfactory in connection with their operability and the performance of their desired objectives, it has been realized that none of such prior art cameras, or devices or systems, are capable of achieving, for example, the aforenoted objectives or operational characteristics of simplicity, accuracy, and reliability required in connection with line scan camera units which are to be utilized within high-speed scanning or processing systems, such as, for example, the sorting or processing of postal mail.
More particularly, in connection with a line scan camera which is to be used to perform, for example, high-speed processing or sorting of postal mail, it has been noted that the camera should be simple, accurate, and reliable. In order to achieve simplicity in connection with the camera structure, for example, it is desirable that the lens have in effect a fixed focal point with respect to the object plane such that the lens need not be refocused each time an object is to be scanned or photographed, or even periodically after repair operations have been completed. Similarly, it is desirable that the camera have its own self-contained illumination system such that exposure adjustments also need not be required each time an object is to be scanned or photographed. In a similar manner, in order to provide the camera with the requisite degree of accuracy, it is desirable to provide the same with a positional calibration system whereby once the lens structure or assembly is positionally calibrated with respect to the object plane so as to fix the focal point, as well as being positionally calibrated with respect to the CCD or charge-coupled device so as to fix the focusing length, positional recalibration of the lens structure or assembly would no longer be required. Such a structural system would therefore obviate currently required setup and calibration procedures by highly skilled technicians and significantly reduce implementation or operational times conventionally required when line scan cameras presently in use are to be used at their field locations.
Still further, it is also noted that line scan cameras which are used, for example, to sort or process postal mail are necessarily subjected to dust and other contaminants which, when collected upon the various optical components of the cameras, compromise or significantly reduce the optical performance of the cameras. In order to rectify this situation, the cameras need to be periodically cleaned or maintained. Such cleaning and maintenance operations or procedures, however, are quite time-consuming, they require skilled technicians to perform such operations or procedures, and in addition, result in significant additional operational downtime of the cameras since the cameras, in addition to the performance of the required cleaning and maintenance operations or procedures, also need to have the lens components positionally recalibrated when the various camera components, which were disassembled in order to perform the cleaning and maintenanced procedures, are to be reassembled with respect to each other.
A need therefore exists in the art for a new and improved line scan camera which is simple in its structural make-up such that, for example, focusing adjustments of the lens assembly with respect to the object plane, as well as exposure adjustments with respect to the object being illuminated and photographed, need not be performed; wherein the positional adjustments for the lens assembly with respect to the object plane and the CCD or charge-coupled device are able to be fixed such that the positional adjustments of the lens assembly with respect to the object plane and the CCD or charge-coupled device need not be recalibrated; and wherein all of the optical components of the line scan camera are disposed within a sealed enclosure such that dust and contaminants attendant the operational usage of the camera are effectively prevented from collecting upon the optical components of the camera such that frequent cleaning, maintenance, and repair of the camera, with comcomitant downtime of the camera system, is effectively reduced or obviated.
Accordingly, it is an object of the present invention to provide a new and improved line scan camera which has particular utility in connection with the scanning or photographing of pieces of mail attendant the high-speed processing or sorting of postal mail.
It is also an object of the present invention to provide a new and improved line scan camera which overcomes the various operational drawbacks and disadvantages characteristic of prior art line scan cameras or similar devices or systems.
Another object of the present invention is to provide a new and improved line scan camera wherein the optical components of the optical assembly of the camera are able to be positionally calibrated relative to the charge-coupled device (CCD) and the object plane of the optical bench such that the optical components need not be recalibrated despite shocks or movement of the camera attendant its normal operations, or even if the camera components are disassembled for the performance of maintenance, cleaning, replacement or repair operations or procedures.
An additional object of the present invention is to provide a new and improved line scan camera wherein the lens structure of the optical assembly of the camera is relatively simple, and the camera is provided with a self-contained illumination system, such that focusing and exposure adjustments need not be performed upon the camera.
A further object of the present invention is to provide a new and improved line scan camera wherein all of the optical components thereof are effectively enclosed within a sealed structure such that dust and other contaminants cannot collect upon and foul the optical components whereby frequent cleaning or maintenance of the optical components of the camera are obviated or significantly reduced.
The foregoing and other objectives are achieved in accordance with the teachings and principles of the present invention through the provision of a new and improved line scan camera which comprises an optical assembly and an optical bench. The optical assembly comprises a printed circuit board upon which is mounted a charge-coupled device (CCD), and a lens assembly which is positionally adjusted or calibrated with respect to the printed circuit board and the charge-coupled device (CCD) such that once the lens assembly is fixed with respect to the printed circuit board and the charge-coupled device (CCD), the focus distance or focus point from the lens to the charge-coupled device (CCD) is fixed. The optical bench comprises an aperture which defines an object plane, and in addition, has a stop block fixedly mounted thereon. The stop block is provided with a plurality of registration surfaces, and the optical assembly is provided with a plurality of set screws which are adapted to be adjusted or calibrated with respect to the registration surfaces of the stop block. When the set screws are properly adjusted or calibrated and fixed in position, the optical assembly is then fixed in position upon the optical bench. In this manner, the lens assembly of the optical assembly is in effect fixed with respect to the object plane of the optical bench such that the focal point or focal distance defined between the lens assembly and the aperture or object plane is fixed. Accordingly, focusing or refocusing of the lens assembly for each or subsequent scanning or photographing operation need not be performed. Similarly, should the optical assembly be disassembled with respect to the optical bench, such as, for example, for the performance of cleaning or maintenance operations, or should the optical assembly need to be replaced with a similarly adjusted or calibrated optical assembly, recalibration of the optical assembly with respect to the optical bench does not have to be performed. It is also noted that all components of the camera are enclosed within a sealed housing structure so as to prevent the ingress of dust or other contaminants into the interior of the housing whereby fouling of the optical components is effectively prevented or substantially reduced, and the forward part of the housing structure is also provided with a self-contained illumination system so as to always adequately illuminate the object plane and the objects being passed across the aperture during a scanning or photographing process. Accordingly, no exposure adjustments are required to be performed.